Nowadays, the commercially available touch screens are classified into several types, including a resistive touch screen, an acoustic wave touch screen, an infrared touch screen and a capacitive touch screen. When an external force is exerted on the resistive touch screen, a voltage is generated and a command is recognized according to the voltage. Moreover, acoustic waves or infrared rays pass over the surface of the acoustic wave touch screen or the infrared touch screen. By touching the surface of the acoustic wave touch screen or the infrared touch screen, the travelling path of the acoustic wave or the infrared ray is blocked and thus the corresponding command is recognized. When the human body is contacted with the capacitive touch screen, the capacitance value of the touch point of the capacitive touch screen is subjected to a change. According to the change of the capacitance value, the touch position is recognized. In views of the touch accuracy and the fabricating cost, the capacitive touch screen is widely adopted.
For complying with the utilized function of the capacitive touch screen, a capacitive touch pen is introduced into the market. Generally, the capacitive touch pen is used for tapping or selecting the capacitive touch screen. In addition, the capacitive touch pen may also have the handwriting and drawing functions. In accordance with the current technology, the capacitive touch pens are classified into two types, i.e. active touch pens and passive touch pens. The passive touch pen has a contact tip made of a conductive rubber. Moreover, the conductive rubber tip is combined with a metallic pen tube. When the conductive rubber tip touches the capacitive touch screen, the electric energy of the human body is transmitted to the conductive rubber tip through the metallic pen tube. Consequently, the capacitance value of the touch point between the capacitive touch screen and the conductive rubber tip is changed.
Hereinafter, the structure of a conventional passive touch pen will be illustrated with reference to FIG. 1. FIG. 1 is a schematic cross-sectional view illustrating a conventional passive touch pen. As shown in FIG. 1, the conventional passive touch pen 1 comprises a pen barrel 10, a conductive rubber tip 11, a coupling ring 12, a positioning screw 13, a supporting seat 14, and a rubber tip supporting member 15. The rubber tip supporting member 15 comprises a supporting ring 151 and a center post 152.
The coupling ring 12 is arranged between the pen barrel 10 and the conductive rubber tip 11. From top to bottom, the components within the coupling ring 12 and the conductive rubber tip 11 comprise the positioning screw 13, the supporting seat 14 and the rubber tip supporting member 15. Moreover, the conductive rubber tip 11 comprises a radial part 111. The radial part 111 of the conductive rubber tip 11 is positioned in the region between a lower stepped part 121 of the coupling ring 12 and a protruded edge 141 of the supporting seat 14.
The rubber tip supporting member 15 is combined with the supporting seat 14. Moreover, the rubber tip supporting member 15 is located at an inner and rear side (i.e. the upper side as shown in FIG. 1) of an arc-shaped end of the conductive rubber tip 11. A first end of the rubber tip supporting member 15 has a center opening, and a distal post 142 of the supporting seat 14 is inserted into the center opening. The supporting ring 151 and the center post 152 are located at a second end (i.e. the lower end as shown in FIG. 1) of the rubber tip supporting member 15. In other words, the supporting ring 151 and the center post 152 are located at the inner and rear side (i.e. the upper side as shown in FIG. 1) of the arc-shaped end of the conductive rubber tip 11.
The positioning screw 13 is penetrated through a center hole of the coupling ring 12 and tightened into a center screw hole of the supporting seat 14. Consequently, the conductive rubber tip 11, the supporting seat 14 and the rubber tip supporting member 15 are assembled with the coupling ring 12 and positioned on the coupling ring 12. Next, an outer screw thread 101 of the pen barrel 10 and an inner screw thread 122 of the coupling ring 12 are engaged with each other. Meanwhile, the passive touch pen 1 is assembled.
After the assembling process of the passive touch pen 1 is completed, the user may touch or slide the conductive rubber tip 11 on the capacitive touch screen. In response to the counterforce provided by the capacitive touch screen, a portion of the conductive rubber tip 11 is subjected to deformation so as to press the supporting ring 151 and the center post 152 of the rubber tip supporting member 15. That is, in response to the counterforce, the supporting ring 151 and the center post 152 are gradually compressed. Consequently, the rubber tip supporting member 15 may provide a resilient restoring force. In response to the resilient restoring force, the conductive rubber tip 11 can be restored to its original shape while maintaining the functions thereof.
However, the conventional passive touch pen 1 still has some drawbacks. For example, the use of the rubber tip supporting member 15 may increase the fabricating cost and the structural complexity of the passive touch pen 1. Therefore, it is an important issue to provide an improved passive touch pen without the rubber tip supporting member 15. Moreover, the conductive rubber tip of the improved passive touch pen can be automatically restored to the non-compressed original shape when the conductive rubber tip is no longer compressed.